THERMOANALYTICAL INVESTIGATIONS ON HETEROCYCLIC ORGANIC-COMPOUNDS .6. SYNTHESIS, CHARACTERIZATION AND THERMAL-DECOMPOSITION OF 1,4-BIS(PARA-FLUOROBENZENE SULFONYL)-2-ALKOXY TETRAHYDROPYRAZINES

Seven derivatives of 1,4-bis(p-fluorobenzene sulphonyl)-2-alkoxy?? tetrahydropyrazines with different alkoxy groups: amyl, n-butyl, 2-butyl, i-butyl, i-propyl, cyclopentyl and cyclohexyl are synthesized by reaction of 1,4-bis(p-fluorobenzenesulphonyl)-2,5-dihydroxypiperazine with the desired alcohol. The title compounds have the general structural formula: [GRAPHICS] The composition and structure were confirmed by elemental analysis. IR spectroscopy NMR spectroscopy and mass spectral analysis. The thermal decomposition of these compounds occurs in three steps: removal of an alcohol, formation of p-fluorobenzenesulphonic acid of its anhydride and evolution of a tetrahydropyrazine ring. Finally, the sulphonic acid of anhydride deteriorates into carbon. Good correlation could be derived between the nature of the alkyl group and the decomposition temperature, with the branched and cyclohexyl derivatives requiring less energy to evolve the alcohol molecule, i.e. branching aids the decomposition.